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Old 10-01-2010, 07:30 PM   #1
One Less Harley OP
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So you want better brake on your R100GS, why not a 4-pot Brembo????

So you want better brakes on your R100GS??? Why not try something already available from BMW????



Like one of these calipers….






The mounting tab spacing of the R100GS caliper is the same as the left 4 pot Brembo from a R1100xx, K1100xx, R1200C or an early R1150GS (up to 11/2001). I can’t take credit for finding out that this works as there are a few references posted here on ADV Rider about the conversion. The only modification needed is to remove 0.158” off the caliper mounting tabs. This keeps the rotor centered to the caliper. I double checked the measurement and came within a few thousandths of and inch….good enough.





One thing that concerned me, was milling that much material would make the tabs too thin.



The stock 2 pot Brembo is 0.489” thick





The left 4 pot Brembo before milling tabs ( 0.609")





Area of material removed (0.158")




Thickness of tab after milling (0.451")







With 0.158" milled off the mounting tabs, the 4 pot Brembo is 0.038" thinner than the stock 2 pot Brembo.


I have 6 calipers, but only one has been modified. I need to double check the fit and centering of caliper to the rotor before having the other five milled.

I have a friend w/ a R100GS who is interested in trying the 4 pot caliper, but I'm waiting on an order of Galfer green pads to arrive. So look for more postings once it is installed. The bike will also (if he wants to spend the money) get a stainless line.
The five other calipers will be offered here with Galfer green pads and stainless lines.
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One Less Harley screwed with this post 06-01-2014 at 07:54 PM
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Old 10-01-2010, 07:40 PM   #2
fishkens
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I'd love one of those fancy calipers since I probably won't be affording the billet unit anytime soon. Price?

Thanks.
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Old 10-01-2010, 07:47 PM   #3
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I don't know as of yet. I need to make sure the 1st caliper is machined correctly. Then need to get all the pads and stainless lines in, plus see what the total machining cost will be. The machinist is quite reasonable though.
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Old 10-01-2010, 07:51 PM   #4
fishkens
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Ahh, so this'll be a turnkey solution. Nice. Keep us posted.

I haven't done a search but is there a preferred pad?
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Old 10-01-2010, 07:56 PM   #5
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I've read ( for what that's worth) the Galfer Green offers good braking. I'll post when converting my friends R100GSPD. I've never ridden a 2 pot Brembo on the GS. So I'll be relying on his impressions.
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Old 10-01-2010, 08:19 PM   #6
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I'm assuming that it'll be an improvement based on this thread (brief mentions of the Brembo arrangement v. the Nissin).

http://www.advrider.com/forums/showthread.php?t=75031
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Old 10-01-2010, 09:23 PM   #7
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I made this mod to my '92GSPD and like the result. I think my caliper is from an R1100R and a friend milled the required amount from the caliper to center it over the disc. I think it's an effective and worthwhile mod. The stopping is much better. Of course the addition of a racetech gold valve contributed also.
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Old 10-01-2010, 09:30 PM   #8
fishkens
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Okay, so now I'm thinking. Does it really need to be milled to be centered over the rotor? I mean, do the pistons really care if the guys on the one side of the are a little bit deeper in their bores and the fellows on the other side are a little bit prouder in their bores? We're talking about 1/16th of an inch on each side.

Hmmmm, just how much do the pistons care if they're all in the same relative position in the bores?

Am I misisng something?
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Old 10-02-2010, 04:26 AM   #9
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Huh ?

Quote:
Originally Posted by ColininKodiak
Assuming the same piston diameter and bore, the pressure would be higher in one cylinder than the opposite side. I'd think this would cause the higher pressure side to wear the pad faster. Centering them causes each side to exert the same pressure and keep pad wear even. I'd also be leery of putting more pressure on one side of the disc as this has the potential to shear it off the hub (in extreme cases).
The pressure in a hydraulic system HAS to be the same all over the piping.

I agree I can't see what diffs it would make for the disk to be off-centre.
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Old 10-02-2010, 04:58 AM   #10
B.Curvin
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Quote:
Originally Posted by ColininKodiak
Assuming the same piston diameter and bore, the pressure would be higher in one cylinder than the opposite side. I'd think this would cause the higher pressure side to wear the pad faster. Centering them causes each side to exert the same pressure and keep pad wear even. I'd also be leery of putting more pressure on one side of the disc as this has the potential to shear it off the hub (in extreme cases).


For future reference, there are no stupid questions, but there are stupid answers.

Did you just make that up as you typed?





Quote:
Originally Posted by espressodrinker
The pressure in a hydraulic system HAS to be the same all over the piping.

I agree I can't see what diffs it would make for the disk to be off-centre.
Yeppers.
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Old 10-02-2010, 05:11 AM   #11
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For future reference, there are no stupid questions, but there are stupid answers.

Did you just make that up as you typed?



Hey you syole my reply. I just wanted to know how the pressure would be greater in one side over the other? I'd love to read the rational. Maybe there is a new field of physics that I am un aware of?
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Old 10-02-2010, 05:42 AM   #12
B.Curvin
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Quote:
Originally Posted by C Squared
Hey you syole my reply.
I saw I had been quoted and thought for sure someone was going to bash me for being an asshole.
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Old 10-02-2010, 06:09 AM   #13
ipanemaguy
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It's not the pressure it's the gap

Quite correctly several have stated that in a hydraulic system the pressure equalizes, hence the inner and outer pistons will have the same pressure if they are driven from the same master.
I will suggest that the problem arises at some off-center differential that the pads on one side may retract insufficiently to completely clear the rotor and result in brake drag, overheating (and consequent warping) of the rotor.
Some difference may be OK, too much is harmful - as is everything else in life.
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Old 10-02-2010, 06:31 AM   #14
One Less Harley OP
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I doubt you could get the pad in the caliper on one side.
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Old 10-02-2010, 07:08 AM   #15
Christos 1983
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i am an owner of a bmw r100gs p-d.i have change the standard calliper with a 4-piston nissin from gsxr 750,i have put metal brake lines and a brake disk from cbr 900.now i have stronger brake but i have more 'travel 'in the brake lever...i want to change the master cylinder to reduce the 'travel' and make the brake feeling more instant.From what bike can i put?the master cylinder from a 1100-1150 is suitable?
thanx guys!

sorry about my english but i am from greece and i have not practised them for a long time....
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